ABSTRACT Summary: This proposal supports a five-year training program for Dr. Sabo to gain the skills she needs to become an independent physician-scientist and an expert in reproductive immunology. Dr. Sabo has a background in basic science and immunology, and plans to shift her focus to clinically-oriented, translational research. She has developed a set of aims that align with her research interests, and six core learning objectives to help her make this transition. Research plan: Bacterial vaginosis (BV) and sub-optimal vaginal bacterial taxa have been associated with HIV acquisition. The precise mechanism by which this occurs is unknown, but may be related to increased cervical inflammation. Dendritic cells (DCs) are critical for regulating the inflammatory state of mucosal tissues, and likely play a role in genital acquisition of HIV. However, DCs remain minimally characterized in the cervix. The purpose of this proposal is to examine if sub-optimal vaginal bacteria and increased vaginal bacterial species diversity are associated with increased total cervical DCs. We have proposed three aims to answer this question. For AIMS 1 and 2, we will perform a cross sectional study of female sex workers (FSWs) enrolled in a longitudinal, open cohort study in Mombasa, Kenya. Vaginal swabs and cervical biopsy samples will be collected at a single visit. To determine if high-risk bacterial taxa are associated with increased DC number (AIM 1), we will evaluate the association between concentrations of vaginal bacteria (measured by quantitative PCR [qPCR]) and total numbers of cervical DCs (measured by flow cytometry from tissue digests of cervical biopsies). To examine the relationship between vaginal bacterial species diversity and cervical DCs (AIM 2), we will perform broad range PCR with high throughput sequencing of vaginal swabs to calculate the Shannon Diversity Index (SDI) for each patient, and the SDI will be compared to the number of DCs isolated by flow cytometry. In AIM 3, we will test the hypothesis that treatment of BV reduces the number of cervical DCs. As an exploratory outcome, DC activation will be assessed by measurement of cell surface co-stimulatory markers and intracellular pro-inflammatory cytokines for all aims. Together, these aims have the potential to provide evidence for a mechanistic link between sub-optimal vaginal microbiota, cervical inflammation, and HIV susceptibility in women. Training plan: The six core learning objectives for this K23 award period include training in epidemiology, clinical studies, global health, high dimensional data analysis, mucosal immunology, and the vaginal microbiome. These goals were selected to ensure that Dr. Sabo acquires the skills necessary to lead her own clinical studies and launch an independent research career performing translational studies to elucidate the role of the reproductive immune system in health and disease. Training to complete the six key learning objectives will be achieved through a combination of mentorship, coursework, implementation of the proposed research plan, local seminars, and national and international meetings. .